Reduced graphene oxide and CdTe nanoparticles co-decorated TiO2 nanotube array as a visible light photocatalyst

TiO₂ nanotube array (TiO₂ NT) was co-decorated by reduced graphene oxide (RGO) and CdTe nanoparticles (NPs) through a simple one-step electrodeposition process. RGO film was formed on the top surface of TiO₂ NT and CdTe NPs homogeneously dispersed within the RGO sheets and on the inner/outer walls of TiO₂ NT. Resulting from the synergetic effect of RGO and CdTe, the photocatalytic activity of the ternary RGO/CdTe–TiO₂ NT photocatalyst far exceeded those of bare TiO₂ NT, RGO-TiO₂ NT, and CdTe–TiO₂ NT photocatalysts in the degradation of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) under simulated solar light or visible light irradiation. After 180-min UV–Vis (or visible light) irradiation, almost 100 % (or 96 %) 2,4-D removal efficiency was achieved on RGO/CdTe–TiO₂ NT, much higher than 42 % (or 2 %) on bare TiO₂ NT, 58 % (or 10 %) on RGO–TiO₂ NT, and 52 % (or 41 %) on CdTe–TiO₂ NT. This study will inspire better design of advanced photocatalysts with high visible-light photocatalytic activity.     

Anodic titanium oxide as immobilized photocatalyst in UV or visible light devices

Titanium anodizing can be a powerful technique to generate photoactive oxides, strongly adherent to the metallic substrate, and to modify their chemical composition by inducing doping effects. This work investigates the photocatalytic behavior of differently obtained anodic TiO(2) films under UV and visible light irradiation, so as to define the best treatment for wastewaters purifiers. Anodizing was performed in H(3)PO(4) and H(2)SO(4) mixtures or in fluoride containing electrolytes. Morphology, elemental composition and crystal structure of the anodic films were characterized by XDR, GDOES and SEM. When amorphous oxides were obtained, an annealing treatment was used to promote the formation of anatase crystals. Annealing was also performed in nitrogen atmosphere to induce nitrogen doping. The photocatalytic efficiency of anatase-enriched TiO(2) was investigated in rhodamine B photodegradation. Doping was induced not only by annealing but also directly by anodizing, and generated photoactivity in both the UV and Vis components of light.     

Sulphur,nitrogen-doped TiO2/graphene oxide composites as a high performance photocatalyst

Sulphur (S), nitrogen (N)-doped TiO₂/graphene oxide (GO) composites were environmentally friendly synthesised using thiourea (CS(NH₂)₂) as a binary-element doping reagent by a simple colloidal blending method. The S, N-doped TiO₂/GO composites show higher photocatalytic degradation rates on methyl orange (MO) compared to TiO₂. The average value of k (the apparent rate constant) for the S, N-doped TiO₂/5%GO (k?=?0.035?min^?1) was found to be eight times higher than that of TiO₂ grown in solution (k?=?0.0038?min^?1) and four times higher than that of P25 (k?=?0.008?min^?1). The investigation showed that the contribution of GO to the high photocatalytic activities of the composites come from its high specific surface area, oxygen-containing functional groups and large aromatic domains that were inclined to be bound by conjugated MO molecules via π–π stacking. The doping of S and N can increase the numbers of photo-generated electrons and holes, which produce more charge carriers to form reactive species, and thus promote the degradation of MO. This work could offer a route to improve the photocatalytic activities of TiO₂ and facilitate their application in reality.     

Ag@graphene oxide nanocomposite as an efficient visible-light plasmonic photocatalyst for the degradation of organic pollutants: A facile green synthetic approach

We report a simple and effective supercritical route to decorate silver nanoparticles (Ag NPs) on graphene oxide (GO) using a commonly available and non-toxic glucose as a reducing agent. Transmission electron microscopy and energy-dispersive X-ray analysis confirmed that Ag NPs of size around 8–20 nm were coated on the GO surface under optimized experimental condition. Ag NPs on the GO surface were predominantly spherical in shape and well dispersed. The experimental results proved that the as-synthesized GO/Ag nanocomposite could be used as a highly efficient photocatalyst for the degradation of Rhodamine 123 dye and acetaldehyde under visible-light irradiation. The degradation results indicated that the photocatalytic performance of nanocomposite was greatly enhanced owing to the improved adsorption performance and separation efficiency of photo-generated carriers. The nanocomposite maintains a high level activity even after four times of recycle. Furthermore, the nanocomposite exhibited excellent antibacterial activity against gram-positive and gram-negative microorganisms.     

Synthesis and characterization of calcium-doped lanthanum manganite nanowires as a photocatalyst for degradation of methylene blue solution under visible light irradiation

Calcium-doped lanthanum manganite (LCMO) powder was synthesized via hydrothermal method. The structural, morphological and optical properties of the resulting powder was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma–atomic emission spectroscopy (ICP–AES spectrometer), field emission scanning electron microscopy (FESEM) and UV–Vis spectroscopy (UV–Vis). The XRD results showed the existence of only one crystalline phase. FESEM image indicates that the LCMO sample has nanowire structure with an average diameter of \(\sim \)125 nm. The band gap energy of the sample was about 2.13 eV. The as-prepared nanowires showed sufficient visible-light photocatalytic activity for the water treatment from dyes and toxic organic materials. The photodegradation efficiency for decolourizing methylene blue solution (7 ppm) by LCMO nanowires \((0.07\hbox {g l}^{-1})\), after 360 min illumination, was about 73% with a reaction rate constant of \(0.003 \,\hbox {min}^{-1}\). The six times cycled results suggested the great long-term stability of the photocatalyst.     

Ti-HMS as a single-site photocatalyst for the gas-phase degradation of benzene

Mesoporous Ti-HMS is able to be used as an active “single-site” photocatalyst for the gas-phase heterogeneous degradation of benzene, a notorious aromatic organic pollutant. In particular, it has been found that Ti-HMS shows enhanced activity and stability toward degradation of benzene as compared with commercial titania (Degussa, P25), which could be attributed to its unique features of large surface area, highly dispersion state of Ti oxide species and mesoporous channel structure. This suggests that there is a promising potential in using Ti-containing molecular sieves as a photocatalyst for degradation of volatile aromatic organic pollutants in air, therefore advancing the applications of such “single-site” photocatalyst in environment cleanup.     

Fabrication of anion exchanger resin/nano-CdS composite photocatalyst for visible light RhB degradation

A novel nanocomposite photocatalyst, D201-CdS beads (0.70-0.80 mm in diameter), was fabricated for visible light (λ > 420 nm) photodegradation of Rhodamine B (RhB). Sphalerite CdS nanoparticles (5-15 nm) were distributed within the outer layer of D201 for favorable visible light permeation. Ultraviolet-visible spectral changes of RhB solution indicated that efficient RhB photodegradation was achieved by D201-CdS under visible light irradiation. More attractively, negligible photocorrosion of the hybrid catalyst D201-CdS was demonstrated by the constant photodegradation efficiency and negligible CdS leaching during five-cycle batch runs. Besides the higher stability, D201-CdS is superior to CdS in terms of separation. The used nanocomposite can be readily separated from solutions by a simple filtration while a high speed centrifugation is needed for the separation of CdS. The above results suggested that the resultant D201-CdS nanocomposite catalyst is promising for practical application in environmental remediation.     

rGO-Bi2MoO6 heterostructure: synthesis,characterization and utilization as a visible light active photocatalyst for the degradation of tetracycline

Journal of Materials Science: Materials in Electronics - This study reports the synthesis of rGO-Bi2MoO6 heterostructure via a simple yet cost effective hydrothermal route and its morphological and...     

Reduced graphene oxide/ZnO nanocomposite modified electrode for the detection of tetracycline

Journal of Materials Science - In this work, rGO-ZnO (reduced graphene oxide–zinc oxide) nanocomposite was prepared and used for modification of GC (glassy carbon) surface in order to obtain...     

Growth of quantum-confined CdS nanoparticles inside Ti-MCM-41 as a visible light photocatalyst

CdS nanocrystallites have been successfully incorporated into the mesopores of Ti-MCM-41 by a two-step method involving ion-exchange and sulfidation. The X-ray diffraction patterns (XRD), UV-vis absorption spectra (UV-vis), photoluminescence spectra (PL), Raman spectra and N₂ adsorption-desorption isotherms were used to characterize the structure of the composite materials. It is found that most of the CdS nanocrystallites are about 2.6 nm, less than the pore diameter of Ti-MCM-41. The CdS nanocrystallites inside the mesopores of Ti-MCM-41 host show a significant blue shift in the UV-vis absorption spectrum. Under irradiation of visible light (λ > 430 nm), the composite material has greater and more stable photocatalytic activity for hydrogen evolution than bulk CdS, which can be explained by the effective charge separation between the CdS nanocrystallites and mesoporous Ti-MCM-41.     

Montmorillonite/graphene oxide nanocomposite as superior adsorbent for the adsorption of Rhodamine B and Nickel ion in binary system

A series of montmorillonite reduced graphene oxide (MrGO) composites were synthesized using different ratios (5, 10, 15 and 20) of montmorillonite (MMt) to GO. The synthesized composites were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, surface area analyzer (BET), and Fourier transform- infrared spectroscopy. The adsorption capacity and efficiency of the synthesised composites were examined towards removal of Rhodamine B (RhB) and Nickel ion (Ni²⁺). The results were compared with that of GO and commercial MMt clay. The kinetic sorption models were evaluated, and it was observed that sorption follows the pseudo-second-order kinetics. Adsorption isotherm was best fit into the Langmuir model (R²?=?0.996 for RhB & 0.957 for Ni²⁺). Among all the synthesized composites, MrGO-2, a composite of GO and montmorillonite with (1:10) ratio, showed maximum activity towards the adsorption of Rhodamine B and Ni²⁺ calculated to be 625?mg/g and 178?mg/g respectively at neutral pH condition. From the calculated ΔG⁰ (?3.99 & ?0.71?kJ?mol^?1), ΔH (28.6 & 4.61?kJ?mol^?1) and ΔS (?107.5 & ?17.8?J?mol^?1 K) values for RhB & Ni²⁺ respectively, it can be unambiguously inferred that the adsorption process was feasible, endothermic and exhibiting least randomness, respectively. The prepared MrGO composites showed good adsorption capacity towards efficient removal of RhB and Ni²⁺ in single as well as binary system.     

Chitosan-functionalized graphene oxide as a nanocarrier for drug and gene delivery

The covalent functionalization of graphene oxide (GO) with chitosan (CS) is successfully accomplished via a facile amidation process. The CS-grafted GO (GO-CS) sheets consist of about 64 wt.% CS, which imparts them with a good aqueous solubility and biocompatibility. Additionally, the physicochemical properties of GO-CS are studied. As a novel nanocarrier, GO-CS is applied to load a water-insoluble anticancer drug, camptothecin (CPT), via π-π stacking and hydrophobic interactions. It is demonstrated that GO-CS possesses a superior loading capacity for CPT, and the GO-CS-CPT complexes show remarkably high cytotoxicity in HepG2 and HeLa cell lines compared to the pure drug. At the same time, GO-CS is also able to condense plasmid DNA into stable, nanosized complexes, and the resulting GO-CS/pDNA nanoparticles exhibit reasonable transfection efficiency in HeLa cells at certain nitrogen/phosphate ratios. Therefore, the GO-CS nanocarrier is able to load and deliver both anticancer drugs and genes.     

Hydrothermal synthesis of nickel iron oxide nano-composite and application as magnetically separable photocatalyst for degradation of Solar Blue G dye

In this research, nickel iron oxide nano-composite was effectively prepared via a simple hydrothermal route in an autoclave at 180?°C. The phase formation and opto-elctronic properties of nano-composite were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), UV–Vis diffuse reflectance spectra (UV–Vis DRS) and vibrating sample magnetometer (VSM) techniques. The VSM reults showed magnetization value of 38.25 emu/g. FTIR and XRD results confirmed the formation of cubic NiFe₂O₄ and rhombohedral Fe₂O₃ phases. The results of FESEM and EDAX studies indicate the formation of nickel iron oxide nano-composite with size of 7–10 nm. UV–Visible diffuse reflectance spectra experimental results showed transition energies of 1.66, 2.5 and 3.7 eV. Additionally, the prepared nickel iron oxide nano-composite were used as photocatalyst for for degradation Solar Blue G dye and the results showed good activity and recyclable by applying an appropriate magnetic field. The reuse of the prepared nickel iron oxide nano-composite for removal of Solar Blue G dye water pollutants was attained in five cycles with an average efficiency of 81%.     

Photocatalytic activity of novel AgBr/WO3 composite photocatalyst under visible light irradiation for methyl orange degradation

A novel AgBr/WO(3) composite photocatalyst was synthesized by loading AgBr on WO(3) substrate via deposition-precipitation method and characterized by XRD, SEM and DRS. The as-prepared AgBr/WO(3) was composed of monoclinic WO(3) substrate and face-centered cubic AgBr nanoparticles with crystalline sizes less than 56.8 nm. AgBr/WO(3) had absorption edge at about 470 nm in the visible light region. The optical AgBr content in AgBr/WO(3) was 0.30:1 (Ag/W) at the corresponding apparent rate, k(app), of 0.0160 min(-1) for MO degradation. The highest k(app) was 0.0216 min(-1) for 4 g/L catalyst. The OH acted as active species. Addition of H(2)O(2) within 0.020 mmol/L can efficiently trap electrons to generate more OH and further improved photocatalytic activity of AgBr/WO(3).     

A platform for electrochemical sensing of biomolecules based on Europia/reduced graphene oxide nanocomposite

This study aimed at preparing and evaluating the europium oxide–reduced graphene oxide (rGO) composites. Inorganic nanoparticles anchored onto rGO sheets through a facile sonochemical method. The resultant products were characterized by FT-IR, XRD, SEM. Their activity in biomolecules’ analysis were examined by cyclic voltammetry. The rectified electrodes revealed an incredibly electroactive manner. The obtained progress provided excellent materials for scrutiny of biomolecules. The linear relationship was used in the region of 100–1500 µM ascorbic acid (AA), 50–600 µM dopamine (DA), and 10–700 µM uric acid (UA), between current intensities and concentrations. The detection restrictions (LOD) (S/N?=?3) decreased to 8 µM, 1.1 µM and 0.085 µM for AA, DA and UA respectively by differential pulse voltammetry (DPV).     

ZnO/Ag nanocomposite: An efficient catalyst for degradation studies of textile effluents under visible light

Degradation of model organic dye and industry effluent was studied using different weight percentages of Ag into ZnO as a catalyst. In this study, the catalysts were prepared by thermal decomposition method, which was employed for the first time in the preparation of ZnO/Ag nanocomposite catalysts. The physical and chemical properties of the prepared samples were studied using various techniques. The specific surface area, which plays an important role in the photocatalytic degradation, was studied using BET analysis and 10 wt.% Ag into ZnO showed the best degrading efficiency. The optical absorption (UV–vis) and emission (PL) properties of the samples were studied and results suggest better photocatalytic properties for 10 wt.% Ag sample compared to other samples.     

Ultrafast degradation of common organic dyes in presence of gadolinium oxide/graphene oxide in water

Gadolinium oxide/graphene oxide (Gd₂O₃/GO) nanocomposite has been prepared by a simple method in N,N-dimethylformamide (DMF) and employed as an excellent catalyst for common organic dyes degradation under ultrasound. The scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS) data revealed that the Gd₂O₃ nanoparticles were successfully attached on the surface of GO sheets. The High efficiencies of common dyes (methylene blue, methyl orange, methyl violet rhodamine B, fuchsin base, thymolphthalein, crystal violet and eosin) degradation within 15?min illustrated that the as-synthesized nanocomposite was an ultrafast, stable, recyclable, and economical material for environment related applications.     

Efficient degradation of environmental contaminants using Pd-RGO nanocomposite as a retrievable catalyst

Clean Technologies and Environmental Policy - Pd nanoparticles (NPs)/reduced graphene oxide (RGO) nanocomposite was prepared in a one-pot process by using Euphorbia stenoclada extract as...     

Three-dimensional magnetic graphene oxide foam/Fe3O4 nanocomposite as an efficient absorbent for Cr(VI) removal

We developed a novel three-dimensional (3D) graphene oxide foam/Fe₃O₄ nanocomposite (GOF/Fe₃O₄) and evaluated its adsorption performance for Cr(IV) removal. The 3D free-standing graphene foam was firstly synthesized on nickel foam and then oxidized and magnetically functionalized with Fe₃O₄ nanoparticles to form GOF/Fe₃O₄. The GOF/Fe₃O₄ exhibited a very large surface area of 574.2 m²/g, a high saturation magnetization of 40.2 emu/g, and a maximum absorption capacity of 258.6 mg/g for Cr(IV) removal, which significantly outperformed the reported 2D graphene-based adsorbents and other conventional adsorbents. The present work may offer a way to prepare a range of 3D magnetic graphene-based adsorbents for application in effective removal of heavy metal ions.